Optical assembly for generating light beams accurately at right-angles to each other

Abstract

An optical assembly is provided which comprises a light source, preferably a laser, and a particularly compensated prism unit, the laser and the prism unit being mounted on a common holder or base. The beam emitted from the laser is reflected 90° by the prism unit, and although this unit is only approximately aligned with the laser the reflected beam will always form a right angle to the incident beam with an extreme accuracy, the deviation from 90° being less than half an angular minute. The accuracy in reflexion independently of prism unit setting is attributed to the compensated prism unit, which comprises a quadrangular prism composed of two semi-quadrangular prisms, a reflecting surface being mounted, preferably in an adjustable position, adjacent one side of the prism.

I claim: 
     
       1. An optical assembly comprising a light source for emitting a collected concentrated light beam and an optical apparatus including (a) a beam splitter in the form of a quadrangular prism composed of two semi-quadrangular prisms having a semi-reflecting transparent region at their common interface, and (b) mirror means located spaced away from and facing one external face of the quadrangular prism; said light source being oriented to direct said light beam toward said optical apparatus to be incident upon the quadrangular prism and to be split thereby into two part beams, one of which after reflection at said mirror means is an emergent light beam angularly deviated relative to said path of the incident beam;   the mirror meand having a position so adjusted relative to the quadrangular prism that said angular deviation is equal to 90° and is constant for a range of angles of incidence of said incident beam upon the quadrangular prism;   a base, said light source and optical assembly being mounted on said base, said optical apparatus being accommodated in a housing, said housing being a part of a deviating unit, said deviating unit being rotatably mounted in a body on said base of the optical assembly, the axis of rotation of the deviating unit substantially coinciding with said incident light beam from the light source.   
     
     
       2. An assembly as claimed in claim 1, wherein said base is provided with a scale impinged upon by said emergent light beam at a certain rotational position of the deviating unit. 
     
     
       3. An optical assembly as claimed in claim 1, wherein the deviating unit, incorporating the relatively positioned prism and mirror means, is removable from the rest of said optical assembly. 
     
     
       4. An optical assembly as claimed in claim 1, wherein said base is arranged for attachment to an elongate member, and is provided with guide means arranged to coact with said elongate member so that, in use, the light beam emitted by the light source will be aligned at right-angles to the direction of said elongate member. 
     
     
       5. An optical assembly as claimed in claim 4, wherein said base of the assembly is provided with attachment means, by which said base is removably secured to said elongate member and rotatable about it whilst maintaining said alignment. 
     
     
       6. An optical assembly for checking alignment of an axle with respect to a vehicle frame, comprising: an elongate barlike base having means adjacent one end for mounting same with respect to one end of said axle for extension along said frame at right angles to said axle;   a light beam source fixed on said base adjacent said mounting means for directing a light beam along said base toward the free end of said base;   first measuring bar means securable transversely on said frame and having a scale spaced from said base and disposed along an extension of the length axis of said base;   second measuring bar means having means adjacent one end for mounting same with respect to the other end of said axle for extension along said frame at right angles to said axle and parallel to said base, and scale means adjacent the free end of said second measuring bar means;   an open ended tubular socket fixed on said elongate base adjacent the free end of said base and substantially coaxial with the path of a light beam from said source;   a housing from which extends a hollow tubular shank coaxial with and rotatably receivable in said socket for mounting said housing substantially coaxially along said light beam;   a quadrangular prism fixedly supported in said housing and comprising two triangular prisms having a semireflecting transparent region at their common interface, with opposed first and second sides of said two triangular prisms substantially on and facing along the longitudinal axis of said housing and the remaining opposed third and fourth sides of said two triangular prisms facing toward the sides of said housing substantially toward and away from, respectively, said scale on said second measuring bar means;   a mirror fixedly supported in said housing between the side of said housing and said fourth prism side and facing substantially toward said scale on said second measuring bar means, the prism being disposed on the path of a light beam from said light beam source, the prism and mirror providing two reflections for a light beam incident on said prism, namely at said interface and at said mirror, to provide an emergent beam angularly deviated from said incident beam and toward said second measuring bar means scale, said mirror being spaced from said quadrangular prism, the position of said mirror in said housing being so preadjusted as to render said angular deviation equal to 90° and a constant for a range of angles of incidence of said incident beam on said quadrangular prism, said housing being optically open toward said scales of said first and second measuring bar means as well as toward said light source, such that emergent light beams at 90° to each other are directed from said housing to the scales of said first and second measuring bar means with greater angular accuracy than required between the faces and interface of said quadrangular prism.   
     
     
       7. An optical assembly, usable as for checking alignment of an axle with respect to a vehicle frame, said optical assembly comprising: an elongate base;   a light beam source fixed on said base adjacent one end of said base for directing a light beam along said base toward the other end of said base;   a body and means fixing said body with respect to said elongate base adjacent said other end of said base and having a portion substantially coaxial with said light beam from said source;   a housing rotatably supported by said body portion substantially coaxially along said light beam from said light source;   a quadrangular prism fixedly supported in said housing and comprising two triangular prisms having a semireflecting transparent region at their common interface, with opposed first and second sides of said two triangular prisms spaced from each other along and facing substantially along the longitudinal axis of said housing and the remaining opposed third and fourth sides of said two triangular prisms facing toward the sides of said housing;   a mirror member fixedly supported in said housing independent of said quadrangular prism, the quadrangular prism being disposed on the path of the light beam from said light beam source, the quadrangular prism and mirror providing two reflections for a light beam incident on said quadrangular prism, namely at said interface and at said mirror member, to provide an emergent beam angularly deviated from said incident beam and directed out the third prism side, said mirror being spaced from said quadrangular prism, the position of said mirror member in said housing being so preadjusted as to render said angular deviation equal to 90° and a constant for a range of angles of incidence of said incident beam on said quadrangular prism, said housing being optically open at said third prism side as well as toward said light source, such that light beams at 90° to each other enter and emerge from said housing with greater angular accuracy than required between the faces and interface of said quadrangular prism.